Railway traffic controlling system



Sept. 10, 1935. s. N. WIGHT RAILWAY TRAFFIC CONTROLLING SYSTEM OriginalFiled Nov. 1, 1929 ATTORNEY 1U mm IAWNE L l 5 HE m5 mm k "m x mn 3 an wm lk1 u FY QNWIPI. d lt U ww mw advantages of Patented Sept. 10, 1935UiTED STT RAILWAY TRAFFIC CONTROLLING SYS TEM

Sedgwick N. Wight, Rochester, N. Y., assignor to General Railway SignalCompany, Rochester, N. Y.

Application November 1, 1929, Serial No. 404,022 Renewed September 20,1932 23 Claims.

This invention relates to approach locking circuits and devices forremote controlled. poweroperated switches, and more particularly tomeans for releasing the approach locking.

For reasons well known to those skilled in the art, it is important thatthe operation of a poweroperated switch, controlled from a distantpoint, should be safe-guarded so that it cannot be operated with a trainapproaching the switch at such a time and under such conditions that theswitch might be unlocked or in mid-stroke when reached by the train.Such a scheme for approach locking protection is shown and described inmy prior application, Ser. No. 120,423, filed July 3, 1926. In such anapproach locking system, and others of a similar type, it is desirableto make provision for energizing a relay or similar electroresponsivemeans, upon movement of a train by a switch; and while this may be doneby utilizing the shunting of the detector track circuit at the switch,as shown in my above mentioned application, it may happen that thedetector track relay is improperly shunted for some reason when a trainis approaching and will cause an improper release of the approachlocking.

In accordance with the present invention, it is proposed to make therelease of the approach locking dependent upon a simultaneous shuntingof two adjacent track circuits, which are both shunted at the same timeduring normal train movements by the switch, so that the accidental orimproper shunting of one of these track circuits will not release theapproach locking.

Various characteristic. features, objects, and

the invention will be in part apparent, and in part pointed out, as thedescription progresses.

The accompanying drawing shows in a simplified and diagrammatic form onespecific embodiment of the invention, the parts and circuits being shownmore with the object of making it easy to understand the principles andmode of operation of the invention, than with the purpose ofillustrating the detail construction of the various devices involved,and the circuit organization preferably employed in practice.

For the purposes of illustration, but not by way of limitation, theinvention has been shown as applied to power-operated switches employedin a centralized control or train dispatching system, and particularlywith respect to the switch at one end of a passing siding PS. Theapproach locking circuits embodying the invention have been illustratedfor the switch SW at the east or rght-hand end of the passing siding PS,This switch is assumed to be operated by a suitable switch machine,preferably of the electrical type, such as shown and described in thepatent to W. K. Howe, No. 1,466,903, dated September 4, 1923. Thisswitch machine (not shown) may '5 be controlled in any suitable mannerby the distant operator, such as disclosed, for example, in my priorapplication above mentioned; and since the specific means employed forthe control of this switch machine, while forming part of the 10complete system embodying the invention, is not material to the approachlocking means constltuting the invention, such control circuits anddevices for the switch machine have not been shown. It is also assumedthat the switch SW 15 will be provided with suitable point detectorcontacts, such as shown, for example, in the patent to Chas. S.Bushnell, No. 1,517,236, dated November 25, 1924, which are operatedautomatically in accordance with the position and 0 locked condition ofthe switch points as operated by the switch machine. Such point detectorcontacts, which may be simple switch circuit controller contacts, areshown diagrammatically as comprising contact members 20 5 and 2|,movable from the normal position shown to a reverse position, therebyopening and closing circuits in a manner which will be evident from thedrawing.

For the purposes of this invention, the insulat- 30 ing joints 55,providing the usual detector track circuit at the switch SW, are solocated and arranged as to provide two separate track circuits havingtrack relays ST and 9AT. With the switch SW in the normal position, thatis, set 355 for the main track, the track relay 9T is shunted by apassing train; whereas with the switch SW in a reverse or take-sidingposition, the track relays ST and SAT are successively shunted by atrain moving onto or off of the siding.

The stretch of track on both sides of the switch SW under considerationis divided into track sections, each provided with a source of current,designated B and a track relay. These track sections are designated 6-l2inclusive, and. their 45 corresponding track relays 6T to IZT.

West-bound trafiic (from right to left) over the switch SW is governedby signals I and IA; and east-bound trafiic by the signals 2 and 2A.Similarly, traffic over the switch at the other end of 50 the passingsiding PS is governed by signals 3-3A and i lA. Signal 5 governswest-bound trafiic approaching this switch SW. These signals may be ofany suitable type, but for simplicity, are assumed to be semaphoresignals. .It is also as- 55 sumed that these signals will beautomatically controlled by track circuits in accordance with thewell-known absolute-permissive-block signal system, subject to manualcontrol by the distant operator or dispatcher, in a manner described inmy prior application above mentioned. For simplicity, in explanation, itis assumed that the signals I-IA and 2-2A will be controlled by a signalcontrol relay ZS of the neutral-polar type, energized over line wires I6and Il from a battery I8 at the dispatchers oflice, in accordance withthe position of the contacts of the control lever L, in a manner as willbe evident from the drawing without detail explanation.

The system of approach locking constituting the invention, consists ofsuitable means for controlling the energization of a lock relay LR,having contact fingers or armatures I8 and I9, which controls theoperation of the switch machine (not shown) in some suitable manner, asby opening the control or operating circuits for the switch machine atthe front contact I9 of lock relay LR,

when it is de-energized. In other words, in con- 7 sidering the natureof this invention and its practical application, it should be understoodthat the lock relay LR, when energized, permits power operation of theswitch SW, providing the detector track circuits are unoccupied, but ifdeenergized, prevents such operation.

The lock relay LR is controlled by approach relays AW and AE and thedetector track relays ST and 9AT, and is dependent upon the position ofthe signals IIA and 22A, and the signal con- .trol relay ZS, all in amanner about to be explained in discussing the operation of the system.

Operation-Considering first the signal control circuits, it will benoted that the west-bound signal I or IA may be cleared, dependent uponthe position of the switch SW and the point detector contact 2 I, over acircuit including wire 24, front contact 25 of line relay II-I, wire 26,polar contact 2? of the signal control relay ZS to the left, wire 28,and neutral contact 29 of the relay ZS.

"The line relay II-I is controlled by a circuit (not shown) controlledby the track relays at the west of the signal I-IA and between thesesignals and the next west-bound signal 33A, as more fully shown in myprior Patent No. 1,294,736, dated Feb. 18, 1919.

Similarly, the east-bound signals 2 and 2A are selectively controlled bythe point detector contact 2|, the line relay 2H, and the polar andneutral contacts 21 and 29 of the signal control relay ZS. It will beevident that the operator by positioning the lever L may energize therelay ZS with current of either polarity, and will thereby causeclearing of either the east-bound or westbound signals, dependent uponthe position of the switch, and providing no trains are presentvde-energizing the line relays IE and 2H. With the relay ZS energizedtoward the right the signals 2 and 2A may be energized through thefollowing circuits:-beginning at the terminal front contact 29 of therelay ZS, wire 28, polar contact 21 toward the right, wire 80, front contact 8! of the relay 2H (assuming trafiic condi- "tions in advance to beclear) wire 82, contact 20, wire 83 and mechanism of signal 2 or wire 84and mechanism of signal 2A depending upon whether the track switch SWrespectively assumes the main track or side track positions, and back tothe other terminal of a suitable battery.

The east approach relay AF. is energized by a circuit which may betraced from B through i the front contact 30 of track relay I2T, wire3|,

front contact 32 of track relay l IT, wire 33, front contact 34 of trackrelay IDT, wire 35, relay AE to C (indicating a common return connectionto the other terminals of the battery).

The west approach relay AW may be energized by either of two circuits,one of which may be traced from B through the front contact 36 of thetrack relay 6T, wire 37, front contact 38 of track relay IT, wires 39and ll], front contact 4| of track relay 8T, wire 42, relay AW to C, and10 the other of which may be traced from B through the point detector orswitch circuit controller contact 43, closed with the switch reverse,wires 4G and 46, then through the front contact 4| of the track relay8T, the same as in the other 15 circuit.

From these circuits just traced it can be seen that a west-bound trainapproaching the switch SW from the east, and closer to the switch thanone track section in the rear of signal 5, deener- 20 gizes the approachrelay AE. An east-bound train, approaching the switch SW from the west,and closer to it than one track section in the rear of the signals L-(lAdeenergizes the relay AW, unless the switch at the west end of thepassing 25 siding PS is in the reverse position, whereupon the relay AWis de-energized only if there is a train on the track section 8.

Assuming that there is no train approaching the switch SW in eitherdirection, so that the re- 30 lays AW and AE are energized, and that thesignals I, IA, 2, 2A are in the stop position, the lock relay LR. isenergized by a circuit which may be traced from front contact 46 of therelay AW, wire 4'1, front contact 48 of relay A151, wires 49 and 50,relay LR, wire 5|, circuit controller 52 of signal IA closed in the stopposition, wire 53, circuit controller 54 of signal I, wire 55, circuitcontroller 56 of signal 2A, wire 51, circuit controller 58 of the signal2 to The relay LR thus once energized is maintained energized by a stickcircuit from through its front contact I8, wires 59 and 50, relay LR andthence to through the circuit controllers 52, 54, 56 and 58 of-thesignals I-IA, 2 and 2A. Thus, while the signals governing traffic overswitch SW are held at stop, a train approaching from either directiondoes not deenergize the relay LR, which is then maintained energized byits stick circuit; and the operator may at any time operate the switchSW. It will be readily appreciated that this arrangement affords thedesired safety, since with the signals I!A and 22A at stop, any trainapproaching will receive a caution or approach restrictive indication atthe signals i and 5 in accordance with established A. P. B. practice,and will slow down and stop before reaching the switch SW, so that theswitch may be properly and safely operated while the train isapproaching. 60

Whenever any one of the signals IIA, or 2-2A is cleared, the lock relayLR is de-energized, and any operation of the switch SW is prevented,until this relay LR is again energized. If there is notrain approachingso as to cause de-energization of the relays AW and AE, the lock relayLR may be energized as soon as the signal cleared assumes its stopposition. Consequently, if the operator should set the switch SW in oneposition or theother, and should clear the corresponding east orwest-bound signals, in anticipation of a certain train movement, andthen should change his mind, he is able to reenergize the relay LR. andoperate the switch by putting his lever L on center to de-energize thesignal control relay ZS and put to stop the signal that he has cleared,provided that no train has in the meantime come within the approachlocking limits and caused de-energization of either of the relays AE orAW.

Considering now the case of a normal train movement over the switch SW,and the manner in which the relay LR is re-energized, or in other words,how the approach locking is released, and assuming a west-bound trainmovement on the main track, the relay LR is re-energiaed as soon as thiswest-bound train shunts the track relays ST and ST by a circuit whichmay be traced as follows:-starting at through the back contact 60 of thetrack relay ST, wires 65 and 62, back contact 83 of relay AW, wire 55,polar contact 65 of relay ZS to the left, wire 65, point detectorcontact 22 normal, wires El, 58 and 58, relay LR, and thence over wire5! through the circuit controllers of the signals I, IA, 2 and 2A, thesignal l assuming its stop position when the train shunts the trackrelay 9T.

Assuming an east-bound train movement on the main track, the operator ordispatcher positions the lever L to energize the signal control relay ZSwith a polarity to clear the signal 2; that is, as shown, the polarcontact 65 of this relay ZS assumes the right-hand position. As thiseast-bound train passes over the detector track circuit 9 and enters thetrack section H deenergizing the track relay NET and consequently theapproach relay AE, a pick-up circuit for reenergizing the lock relay LRis established, the signal 2 being caused to automatically assume itsstop position by the entry of the train into the detector track circuit9, this because the signal 2 is controlled by the home relay 2H whichrelay in turn has included in its energizing circuit a front contact(not shown) of the relay QT, said circuit being traced as follows:-starting at through the back contact Si! of the detector track relay 9T,wires 65 and 10, back contact H of the relay AE, wire '52, polar contact65 in the right-hand position as shown, wire 65, point detector contact22, wires 6?, 58 and 59, relay LR, wire 5!, and thence through thesignal circuit controllers 52, 5d, 5 5 and 58 to Considering now awest-bound train movement onto the siding PS, that is, over the switchSW in its reverse position, in this case, the release locking circuitfor re-energizing the relay L starts at through the back contact E3 ofthe track relay 9A1", wire '56, back contact id of the track relay 9T,wire point detector contact 22 in the reverse position, wires l'i, 68and to, relay LR, and wire 5! through the signal circuit controllers tonegative, in the same way as the other circuits above traced. Inpractice the points of the switch SW are bonded to the rails of thetrack circuit containing track relay QT, so that even the shortestrailway car into the side track will simultaneously de-energize thetrack relays HT and 8A1, from which it is apparent that each entrance ofa train into the side track will result in simultaneous de-energizationof the reiays 9T and EAT.

An east-bound train, moving oif of the siding onto the main track, inksup the relay LR in the same way by the simultaneous de-energization ofthe track relays ST and BAT.

As already noted, the track relays ST and SAT are connected to separatetrack circuits one including the track rails of the main track oppositethe switch SW, nd the other track rails of the end of the passingsiding, up to or beyond the fouling point, the arrangement of insulatedjoints, the track batteries, and relay connections for suchanarrangernent of track circuits being well known and familiar'to thoseskilled inthe art. 5

'It will be noted that the release of the approach locking is dependentupon the simultaneous shunting of the two track relays, as QT and 8'1;and this is one of the important characteristic features of theinvention. Assuming that T0 the re-energization of the relay LR in thecase of a west-bound train on. the main track, above just explained,were dependent merely upon the shunting of the detector track relay 9T,if the west-bound train had passed the signal '5 and was approaching theswitch SW at high speed, the detector track relay 91'' might beaccidentally or improperly shunted for some reason, putting the signal 5to stop and energizing the relay LR to permit operation of the switch SWin the face of '20 the train approaching at high speed. While suchimproper shunting of the track relay QT is remote, there are specialcircumstances under which this may occur, perhaps due to a temporarytrack J circuit failure, careless manipulation by a main" tainer, or thelike. Such shunting of the detector track relay 9T, under the conditionsjust described, would tend to bring about an unsafe condition, not onlybecause the approach locking would be improperly released, but also because the dispatcher, thinking that the indication resulting from theshunting of the track relay 9T signified the arrival of the expectedtrain, would be expected to operate the switch control lever. By makingthe re-energ'ization of the lock relay LR dependent upon thesimultaneous shunting of two track relays, in accordance with thisinvention, it will be evident that the possibility of such dangerouscondition is greatly minimized, if not entirely eliminated, since 150 itis most unlikely that two track circuits will fail at the same time orbe carelessly shunted by a maintainer.

It will be noted that two different track relays are employed forreleasing the approach locking 15 in the case of a west-bound train onthe main track, an east-bound train on the main track, and a trainentering or leaving siding, namely track relays 8T and ST, WT and 9'1,and QAT and 9T, respectively, and it will be observed that the two trackrelays effective to release the approach locking are selected by thepolar contact 65 of the signal control relay ZS and the position of thepoint detector contact 22. In other words, W the position of the switchpoints (contact 22) and the direction of train movement (polar contact65 of relay ZS) determine which two track relays are eifective to causere-energization of the lock relay LR. After a little consideration, itwill be evident that such selection is necessary to obtain the desiredprotection in the release of the approach locking. For example, if therelease of the approach locking were dependent upon track relays ST andMT, for trains moving in either V direction, the detector track relay 9Tmight be improperly shunted with a west-bound train approaching at highspeed and enterirr the track section it), thereby causing an improperrelease of the approach locking. Such contingency is avoided by makingthe release of the approach looking dependent upon the detector trackrelay 9'1 and the track relay of the track section in advance thereof,depending upon the direction of the train movement, so that there is noM release unless the approaching train has passed over the detectortrack section 9, which of course does not occur unless one of thesignals governing traflic over the switch SW is in the clear position,and opposing train movements are blocked.

In the case of a train movement onto the siding, since the siding is notusually equipped with track circuits, it is not possible to obtain thecooperation of the detector track relay ET, and a track relay of a tracksection next in advance thereof, to provide the release for the approachlocking, so that the extra track circuit, with its track relay SAT isprovided at the switch; and these same two track relays QT and SAT areemployed for releasing the approach locking by a train movement on ofthe .siding.

The approach relay AW is controlled by the contact 43 of the switch atthe other or west end of the siding PS, in order that an east-boundtrain taking the siding will not cause approach locking of the switchSW, it being permissible for the operator to retain control of theswitch SW in such a case, since movements on the siding are low speedmovements. For a high-speed eastbound movement, however, the control forthe relay AW should extend to at least one track sec tion in the rear ofthe signal 4-4A, to provide the proper approach locking limits; and ifit were not for the contact G3 and its associated shunt circuit, aneast-bound train entering the siding, would look up the switch SW, andduring its normal movement would not release this approach looking, withthe result of unnecessarily restricting control of the switch by theoperator.

While I have shown and described one specific embodiment of theinvention applied to a switch for a passing siding on a railroadequipped with a centralized control or dispatching system, it should beunderstood that the invention is not .iimited to this particularapplication, or to the pick-up circuit for said stick relay closed onlyupon simultaneous shunting of two different but adjacent track circuits.

2. In a system of approach locking, the combination with apower-operated switch, of signals for governing traffic over saidswitch, a lock relay which must be energized to permit power operationof a railway track switch, and a particular energizing circuit for saidrelay closed only when said signals indicate stop and two differenttrack circuits adjacent the switch 'are simultaneously shunted.

3. In a systern of the character described, a power-operated switch overwhich traflic may move in opposite directions, a lock relay controllingthe operation of said switch, a detector track circuit, track circuitsadjacent to said detector track circuit on each side thereof, twoenergizing circuits for said lock relay each closed when the detectortrack circuit and an adjacent track circuit in advance thereof areclosed, and means depending upon the direction of train movement towardthe switch for rendering one I or the other of said circuits effectiveto control said lock relay.

4. In a system of the character described, a power-operated trackswitch, two track circuits at the switch, one in the main track and theother in the turn-out track, a lock relay which must be energized topermit power operation of said switch, an energizing circuit for saidrelay closed only when said two track circuits are concurrently shunted,and means for rendering said circuit effective to energize said relaywhen the switch is in the reverse position.

5. An approach locking system for poweroperated switches over whichtrains may move in either direction comprising, a lock relay, anenergizing circuit for said relay, and means dependent upon the positionof the switch and the direction of train movement over theswitch forclosing said circuit and effective only when two adjacent track circuitsassociated with such switch are simultaneously shunted.

6. A system for releasing approach locking of the character describedcomprisingin combination with a detector track circuit and other trackcircuits adjacent thereto, a lock relay having a plurality of energizingcircuits, each of said circuits being dependent upon simultaneousshunting of said detector track circuit and a different one of saidadjacent track circuits, and means depending upon the direction of trainmovement over the switch and the position of said switch for selectingthe circuit effective to energize said relay.

"7. In a system of approach looking for poweroperated switch machines,the combination with a lock relay of the stick type which must beenergized to permit operation of such poweroperated switch, signalsassociated with said switch, a pick-up circuit for said relay closedonly if said signals are at stop and two different track circuitsadjacent said switch are simultaneously shunted, and a stick circuit forsaid relay including its own stick contact and closed if said signalsare at stop.

8. In a system of approach looking for poweroperated switch machines,the combination with a lock relay of the stick type which must beenergized to permit operation of such powercperated switch, a detectortrack circuit associated with said switch, a track circuit in advanceand in the rear of said detector track circuit, and two pick-up circuitsfor said lock relay one including contacts closed when said detectortrack circuit and the track circuit in advance are simultaneouslyshunted and the other including contacts closed if said detector trackcircuit and the track circuit in the rear are simultaneously shunted.

9. In a system of approach looking for poweroperated switch machines,the combination with a lock relay of the stick type which must beenergized to permit operation of such power operated switch, signalsassociated with said track switch, an approach section, an approachrelay having an energizing circuit closed when said approach section isunoccupied, and two pick-up circuits for said lock relay one includingsignal contacts closed when said signals are at stop and a front contactof said approach relay in series and the other including said signalcontacts and contacts closed only when two different track circuitsadjacent said switch are simultaneously shunted.

10, In a system of approach looking for poweroperated switch machines,the combination with a, lock relay of the stick type which must beenergized to permit operation of such poweroperated switch, signalsassociated with said track switch, an approach section, an approachrelay having an energizing circuit closed when said approach section isunoccupied, two pick-up circuits for said lock relay one includingsignal contacts closed when said signals are at stop and a front contactof said approach relay in series and the other including said signalcontacts and contacts closed when two different track circuits adjacentsaid switch are simulta neously shunted, and means for selecting saidpick-up circuits in accordance with the position said switch isassuming.

11. In a system of approach looking for poweroperated switch machines,the combination with a lock relay of the stick type which must beenergized to permit operation of such power-operated switch, signalsassociated with said switch, a pick-up circuit for said relay closedonly if said signals are at stop and two different track circuitsadjacent said switch are simultaneously shunted, a stick circuit forsaid relay including its own stick contact and contacts closed if saidsignals are at stop, and means for rendering said pick-up circuiteffective only if said switch assumes a particular position.

12. In combination, a railway track switch, signals associated with saidswitch for governing trafiic in opposite directions over said switch, alock relay which must be energized to permit operation of said switchfrom a remote point, two approach sections one on each side of saidswitch, a control relay for controlling the clearing of said signals andpermitting clearing of a signal for one direction of traffic at one timeonly, and an energizing circuit for said lock relay closed only if theapproach section for the opposite signal from the one selected by saidcontrol relay is occupied and including a contact of said control relayclosed when said one signal is selected for clearing.

13. In combination, a railway track switch, signals associated with saidswitch for governing traffic in opposite directions over said switch, alock relay which must be energized to permit operation of said switchfrom a remote point, two approach sections one on each side of saidswitch, a lever for clearing one of said signals, and an energizingcircuit for said lock relay closed if said lever is in a, position toclear said one signal and the approach section in advance of said onesignal is occupied by a train.

14. In combination, a railway track switch, signals associated with sm'dswitch for governing tralhc in opposite directions over said switch, alock relay which must be energized to permit operation of said switchfrom a remote point, three approach sections one in each track leadingto said switch, a, lever for selecting signals for governing traffic inone direction or the other over said switch, contacts associated withsaid track switch for selecting the proper route signal of the signalsselected by said lever, and a circuit for said lock relay closed if theapproach section in advance of the selected route signal is occupied.

15. In combination, a railway system having a passing siding, a trackswitch at each end of said passing siding, a lock relay for one of saidtrack switches which permits operation of such one switch from a remotepoint only if said lock relay is energized, and means for controllingsaid lock relay by circuits including contacts respeca traific route, astick relay which allows the establishment of said route if and onlyifsaid 5 stick relay is energized, two adjacent track circuited tracksections in another route having a portion in common with said firstmentioned route each section including a normally energized track relay,and a pick-up circuit for said stick 10 relay including two contacts inseries one of which is closed upon occupancy of one of said tracksections and the other of which is closed upon occupancy of the other ofsaid track sections. 5

17. In combination, a track switch, a railway system including a trafficroute, a stick relay which allows the estabishment of said route if andonly if said stick relay is energized, two adjaccnt track circuitedtrack sections in another 20 route having a portion in common with saidfirst mentioned route each section including a normally energized trackrelay, and a pick-up circuit for said stick relay including two contactsin series one of which is closed upon occupancy 5 of one of said tracksections and the other of which is closed upon occupancy of the other ofsaid track section and also including a contact closed only if saidtrack switch assumes a particular position. 3Q

18. In combination, a railway signal, an approach track circuit for saidsignal including a track relay, a second and a third track circuit eachof which includes a track relay, an approach locking relay, a circuitfor said approach locking relay controlled by said approach track relay,and a second circuit for said approach locking relay including a backcontact of said second track relay in series with a back contact of saidthird track relay and controlled by said 40 signal.

19. In combination, a railway signal, an approach track circuit for saidsignal including a track relay, 2, second and a third track circuit eachof which includes a track relay, an approach looking stick relay, apick-up circuit for said approach locking relay controlled by saidapproach track relay, 3, second pick-up circuit for said approachlocking relay including a back contact of said second track relay'inseries with a back contact of said third track relay, and a stickcircuit for said approach locking relay controlled by said signal.

29. In combination, a section of railway track containing a switch, anapproach section adjoin- 5 ing said switch section, a, second approachsection adjoining said switch section, a signal for governing traflicmovements over said switch, an approach locking relay, a circuitcontrolled by traffic conditions in said first approach section andincluding the winding of said relay for controlling said relay, a secondcircuit controlled jointly by traffic conditions in said switch sectionand traffic conditions in said second approach section and including thewinding of said relay for controlling said relay, a third circuitcontrolled by said signal for controlling said relay, and meanscontrolled by said relay for controlling said switch.

21. In a system of the character described, a power-operated trackswitch, two track circuits at the switch one in the main track and theother in the turn-out track, a lock relay which must be energized topermit power operation of said track switch, an energizing circuit forsaid lock relay closed only when said two track circuits are shuntedconcurrently, and means for rendering said circuit eiiective to energizesaid lock relay only when the switch is in the turn-out position.

22. In a system of the character described, a power-operated trackswitch, a detector track circuit associated with said track switch,another track circuit in a track section adjacent said detector trackcircuit, a stick lock relay for when deenergized preventing poweroperation of said track switch, a pickup circuit for said stick relayincluding contacts closed only if both of said track circuits aresimultaneously occupied, and a stick circuit for said stick relay closedonly if a signal for governing movement of traffic over said switch isat stop.

23. In combination, a passing siding of a rail aoiftei way system andHaving a track switch at each 'end thereof, a switch machine for poweroperating one of said track switches, a lock relay which must beenergized to permit power operation of said one track switch, twoapproach sections one reflecting track occupancy in the single tracksection facing the points of said one track switch and the otherapproach section reflecting track occupancy of the main track of saidpassing siding, means for extending said other approach section beyondthe limits of said passing siding and into the single track sectionfacing the points of the other track switch when said other track switchassumes the main track position, and an energizing circuit for said lockrelay closed only 15 if both of said approach sections are unoccupied.

SEDGWICK N. WIGHT.

